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NERVOUS CENTRES. (Human Anatomy. Tue Encepuaton.) 
ard to the outside of the thalamus. It is pear- 
shaped : its thick end is directed forwards and 
inwards, and it gradually tapers backwards 
into a caudate process of considerable length, 
which winds downwards, forwards, and inwards 
into the descending cornu of the lateral ventricle, 
at the anterior extremity of which it terminates. 
Placed on the outside of the thalamus, it seems 
to embrace it there, and to adhere very inti- 
mately to it. The tenia semicircularis lies in 
@ groove between the two bodies, and as it 
were constricts their connecting fibres. 
he corpus striatum is of a dark grey colour. 
A considerable portion of it projects free into 
the cavity of the ventricle, forming an extensive 
convex surface there. The rest is firmly im- 
bedded in the fibrous substance of the hemi- 
sphere, and in position corresponds to the base 
of the insula, which for that reason has been 
called the lobule of the corpus striatum. The 
free surface as contributing to form the ventri- 
cular wall is covered by the lining membrane 
of the ventricle and a layer of nucleus-like 
particles; it is traversed by several veins. This 
surface is limited on the outside by the plane 
of fibres, which, after emerging from it, incline 
inwards and contribute to form the corpus cal- 
 losum. On the inside it is limited by the tenia 
semicircularis, which separates it from the optic 
thalamus. That portion of the free surface 
which is seen in the inferior horn of the ven- 
tricle has, as already stated, the appearance of 
a caudiform prolongation of the upper portion ; 
this probably arises from the diminution of the 
body in thickness at its inferior part, the portion 
which belongs to the inferior cornu forming the 
apex of a cone, of which the upper convex 
portion forms the curvilinear base. 
When sections are made through the corpus 
_ Striatum, it is found to be traversed by very 
humerous bundles of fibres. It is necessary 
that these sections should be directed obliquely 
_ from below upwards in a direction parallel to 
the inferior layer of the crus cerebri. The 
bundles are thicker and more closely approxi- 
mated to each other inferiorly; but as they 
ascend, they diverge, and radiate, some for-’ 
wards, others outwards, and others backwards ; 
some pass nearly vertically upwards. A section 
made ee in the horizontal direction cuts all 
these fibres more or less transversely, so that 
the cut surface presents a grey colour inter- 
Spersed with white spots of variable size, ac- 
cording as the bundles have been cut trans- 
versely or obliquely; but when the section is 
made in the oblique direction, as above di- 
tected, then the surface presents a striated ap- 
pearance like numerous and regular white 
veins in a dark marble, the bundles of fibres 
being cut lengthways. 
In tracing the bundles of fibres through the 
corpus striatum, we find that they divide and 
subdivide and occasionally anastomose. Each 
subdivision becomes clothed as it were with 
grey matter, which fills up the space between 
it and the adjacent ones. The grey matter en- 
sheathes these bundles of fibres, as the areolar 
_ tissue does the fascicles of coarse muscles, and 
699 
it may be dissected away from them, as we 
remove the areolar tissue from the muscular 
bundles. 
It is an important problem to determine the 
exact source of these fibres and their precise 
destination. There can be no doubt that many 
of them are continuous with the inferior plane 
of the crus cerebri. Of those, the major part 
are usually supposed to pass through to the 
white substance of the hemisphere, and some 
no doubt proceed no farther than the corpus 
striatum. The other fibres which are found in 
this body may be viewed as taking their point 
of departure from its vesicular matter, and 
radiating, some outwards into the centrum 
ovale, others backwards to the optic thalamus, 
forming a bond of connection with that body. 
It must be borne in mind that, as the corpus 
striatum is a body of considerable thickness, 
these fibres which emerge from it must pro- 
ceed in very different planes and with varying 
degrees of obliquity. Other fibres are found 
in the corpora striata, which however do not 
contribute to its striation. These are the fibres 
of the anterior commissure. 
From a comparison of the small amount of 
fibrous matter in the inferior plane of the crus 
cerebri with the immense mass which forms 
the white substance of the hemispheres, (even 
if we exclude those fibres which form com- 
missures,) it is impossible to suppose that the 
latter is derived from the former only; nor, 
indeed, can it be admitted that even the greater 
part of the fibrous matter of the hemispheres 
is continuous with that of the crura, whether 
on their superior or inferior plane. A con- 
siderable portion of them doubtless, when traced 
from the hemispheres downwards, will be 
found not to pass below the corpora striata 
or optic thalamus. 
We may regard the corpus striatum as a 
mass of grey matter with fibres implanted 
in it which connect it with the other parts 
of the encephalon. These parts are, ist, the 
hemispheres; 2d, the optic thalami; 3d, the 
crura cerebri, mesocephale, and medulla ob- 
longata. Of these last fibres it is probable, 
(but I am disposed to think far from certain,) 
that some of those which form the inferior 
layer of the crus pass through the corpora 
striata, and diverge among the other fibres of 
the centrum ovale. 
Thus the corpora striata are connected to the 
optic thalami by fibres which pass from their 
concave or inner border to those bodies; to the 
convolutions of the brain by fibres continuous 
with some of those which form the white sub- 
stance of the hemisphere, and we have seen 
that the convolutions of the insula have a very 
close relation to them; to the mesocephale and 
medulla oblongata by the fibres which form the 
inferior layer of the crus; and to each other by 
those which, emerging from them, contribute 
to form the corpus callosum, and also by the 
anterior commissure. 
The vesicular matter of the corpora striata 
does not differ from that of the convolutions, 
It is traversed by a multitude of fibres. These, 
